1. Field of the Invention
The present invention relates generally to static structures, particularly traffic-carrying surfaces, and also relates generally to exercising devices, particularly gymnastic equipment.
2. Description of the Related Art
Helipads used for both civilian and military applications have usually consisted of an asphalt or concrete substrate that is coated with urethanes of various colors to form a predetermined pattern. The urethane coatings are generally applied just 1/64 inch (8 millimeters) thick and, consequently, provide no significant benefit other than clearly marking a landing zone.
Also, school playgrounds, day care centers, playlands adjacent to fast food restaurants, and the like, maintain exercising equipment for children's recreational activities. The activities in these designated play zones include climbing, jumping and swinging, and oftentimes result in falls to the ground. In fact, 70% of playground injuries are the result of impacts to the underlying surface.
Play on sports surfaces for games, such as football, soccer and baseball, is also likely to produce falls but is carried out on fields that are usually constructed of artificial turf laid over an attenuating base.
Before the advent of artificial turf, natural grass was grown as a surface underneath playground equipment and athletic fields. Unfortunately, natural grass requires constant maintenance and varies in its shock attenuating ability. Furthermore, erosion, puddling and sanitation are major negative factors militating against the use of natural grass.
In the search for an answer to the problems posed by natural grass, loose-fill materials and unbonded particles, such as wood chips and sand, were placed under playground equipment to a depth averaging twelve inches. The material was usually contained by a wooden or concrete border. Although loose-fill materials provided excellent attenuating characteristics, it is difficult to maintain them at the proper depth and to keep them free of contamination. Changes in depth and infiltration by debris adversely affect the attenuating properties of such loose-fill materials.
With a desire for a more permanent and consistent surface, non-loose-fill surfaces in the nature of processed particles bonded together in some fashion were developed to be installed over hard surfaces, such as concrete and asphalt. Nonloose-fill surfaces, which are generally referred to as synthetics, can be divided into two main categories: systems with seams and systems without seams. Examples of systems with seams or so-called nonseamless systems are shown in U.S. Pat. Nos. 4,557,457 to Donovan, 3,846,945 to Roby, 3,251,076 to Burke, 2,999,431 to Mitchell, and 957,387 to Stedman.
Both nonseamless and seamless surfacing systems have an attenuating element and a surface layer. This surface layer can be either installed in the field or integrated at the time of manufacture. However, the seamless systems have a texture coat of sealer and aggregate applied over the surface layer to form a monolithic arrangement. Seamless surfacing systems are becoming the more desirable of the synthetic systems because insects and rodents cannot enter and nest in them, nor can dirt and debris collect in the seams. An additional benefit of seamless surfacing systems is that water is not allowed to enter into the system. Water, when introduced into the system, can cause structural deterioration and delamination of the surface system from its subbase.